XF 1.4"Email address banned by administrator" error at signup

Well-known member

I recently sent an email to all the members who've opted to receive emails from administrator. One of the recipients wrote back saying that he does not remember signing up on our site and further said that he tried to create a new account and the registration page showed following error message:-

"The email address you entered has been banned by the administrator. Please try another."

I searched for the signup using his email ID; and was surprised that there actually is no user with that email ID! (I checked for banned email IDs list too). The ID is from 'gmail' and of course it's not in my banned email ID list.

Note: I used 'Sendy' to send email - that uses old user database.

Questions:

1. The only case I'd imagine is that this user was banned and subsequently deleted from our database. Does XF retain a list of banned user emails to prevent them from registration in future?

2. Since I'm unable to 'unban' him (he is not searchable!); how can I allow him to create a new account using his email ID?